A Series of POM–Viologen Photo-/Electrochromic Hybrids and Hydrogels Acting as Multifunctional Sensors for Detecting UV, Hg²⁺, and Organic Amines

In this work, POM anions were introduced into the viologen system in order to synthesize POM–viologen hybrid compounds with excellent properties. Three new POM–viologen compounds, {CdII(tybipy)(DMF)2[β-Mo8O26]0.5Cl} (1), {CoII(tybipy)2(DMF)2[H2(β-Mo8O26)]2}·4C2H7N (2), and (tybipy)4·(β-Mo8O26) (3) (tybipy·Br = 1-thiophen-3-ylmethyl-[4,4′]bipyridinyl-1-ium bromide), have been prepared by a solvothermal method, and their structures were characterized. POM anions are modified by mixing organic ligands with transition metals in compounds 1 and 2. However, compound 3 is a supramolecular structure constructed by hydrogen bonding interactions between the dissociative viologen and POM anions. These three compounds have rapid photoresponse and photochromic ability, which can be made into mixed matrix membranes and hydrogels for UV detection. The rigid sandwich devices prepared by compounds 1–3 have achieved ultrafast electrochromism and recovery. In addition, photochromic hydrogels based on compounds 1–3 can achieve ultrafast photochromic recovery. Compounds 1–3 can be used in ink-free printing and Hg2+ fluorescence detecting. Compounds 1 and 2 can also be used as organic amine detectors. Combined with photochromism and fluorescence detection of Hg2+, visual test papers for Hg2+, Cu2+, and Co2+ were successfully realized, which can improve the portability and detection speed of heavy metal ions in the actual environment

Introduction of secondary pyridyl-1H-tetrazole derivatives into Keggin–Ag–(1,10-phenanthroline) system for tuning dimensionalities and architectures: assembly and properties

<p>By introducing three pyridyl-1H-tetrazole derivatives to Keggin–Ag-(1,10-phenanthroline) system, five new polyoxometalate-based inorganic–organic hybrid compounds with different dimensionalities and structures, [Ag₃(4-ptz)₂Na(phen)(HPMo₁₂O₄₀)]·2H₂O (<b>1</b>), [Ag₄(3-ptz)₂(phen)₂(HPMo₁₂O₄₀)] (<b>2</b>), [Ag₄(3-ptz)₂(phen)₂(HVW₁₂O₄₀)] (<b>3</b>), [Ag₃(3-bptzb)(phen)₂(PMo₁₂O₄₀)] (<b>4</b>) and [Ag₃(3-bptzb)(phen)₂(VW₁₂O₄₀)] (<b>5</b>) (phen = 1,10-phenanthroline, x-ptzH = 5-(x-pyridyl)-1H-tetrazole (x = 3, 4), 3-bptzb = 1,4-bis(5-(3-pyridyl)-tetrazolyl)butane), have been synthesized under hydrothermal conditions. Compound <b>1</b> is a 1-D belt architecture constructed from an Ag-4-ptz metal–organic chain and two Ag–PMo₁₂O₄₀–Na–phen inorganic–organic chains. When 3-ptzH was introduced as secondary ligand in <b>2</b> and <b>3</b> instead of 4-ptzH, two isostructural architectures were obtained, which contain a 1-D zigzag Ag-3-ptz chain with phen ligands hanging on both sides of the chain. The Keggin anions connect adjacent Ag-3-ptz chains to construct 2-D networks. When the flexible 3-bptzb was selected, isostructural <b>4</b> and <b>5</b> with 2-D networks were obtained, which were constructed from binuclear subunits and Keggin–Ag inorganic chains. The influence of three pyridyl-1H-tetrazole derivatives as secondary ligands on the dimensionalities and architectures of <b>1</b>–<b>5</b> was discussed. The electrochemical and photocatalytic properties of the compounds were investigated.</p

Photo-, Thermo-, Electrochromic, Erasable Inkless Printing, Ions Detection, and UV Detector Properties of Viologen Compounds Based on Homomolybdate/Keggin POMs

Three POMs-based viologen compounds with different structures were successfully constructed under solvothermal and hydrothermal conditions, [Cu(1,4-cby)2(H2O)0.5(β-Mo8O26)0.5]·C3H7NO·3H2O (1), [H2(1,4-cby)2]·(β-Mo8O26) (2) (1,4-cby·Cl = 1-(4-carboxybenzyl)-4,4′-bipyridine chloride), [H2(1,4-cbyy)2]·(SiMo12O40) (3) (1,4-cbyy·Cl = 1-(4-cyanobenzyl)-4,4′-bipyridine chloride). Compound 1 is a structure with the number “eight-like” metal–organic chain with Cu as the nodes, and compounds 2 and 3 are fascinating structures connected by hydrogen bonding interactions. More importantly, compounds 1–3 exhibit a good response to both light and electricity and the thermal response of compound 1 was also studied. The reasons for the response of compounds 1–3 to external stimuli were analyzed through methods such as UV–Vis, EPR, and XPS. In addition, the transient photocurrent response results of compounds 1–3 are the same as those obtained from kinetic calculations. Meanwhile, the coated filter paper based on compound 3 has been successfully applied in erasable inkless printing and anti-counterfeiting, the test paper of 3 can also detect metal ions, and the films based on compounds 1–3 are a flexible and portable ultraviolet (UV) detector

Flexible bis(pyridyl-tetrazole) ligand-induced ring-containing metal–organic coordination polymers: synthesis, structures, and properties

<p>Three coordination polymers (CPs), [Co(3-bptzp)(BDC)] (<b>1</b>), [Zn(3-bptzp)(BDC)] (<b>2</b>), and [Cd(3-bptzp)(BDC)] (<b>3</b>) (3-bptzp = 1,4-bis(5-(3-pyridyl)tetrazolyl)propane, H₂BDC = 1,3-benzenedicarboxylic acid), were synthesized under hydrothermal conditions. The CPs were structurally characterized by single-crystal X-ray diffraction, infrared spectroscopy (IR), elemental analyses, and powder X-ray diffraction (PXRD). Complexes <b>1–3</b> represent the first examples of CPs based on the flexible bis(pyridyl-tetrazole) 3-bptzp. Structure analyses reveal that <b>1–3</b> are 1-D ring-containing polymeric chains. For <b>2</b> and <b>3</b>, adjacent 1-D chains are extended to 2-D supramolecular networks by hydrogen bonding. Dye adsorption properties of <b>1–3</b>, electrochemical properties of <b>1</b>, and fluorescent-sensing behaviors of <b>2</b> and <b>3</b> have also been investigated.</p

The rigid isomeric 5-(x-pyridyl)-1H-tetrazole ligands-directed various isopolymolybdate-based compounds: Assembly, structures and properties

<div><p></p><p>Two new isopolymolybdate-based metal-organic complexes, [Cu₂(2-ptz)₂(Mo₄O₁₄)_0.5] (<b>1</b>) and [Cu₃(OH)₂(3-ptz)₄(γ-H₄Mo₈O₂₆)(H₂O)₄]·10H₂O (<b>2</b>) (2-ptzH = 5-(2-pyridyl)-1H-tetrazole, 3-ptzH = 5-(3-pyridyl)-1H-tetrazole), constructed from isomeric ligands with different N-donor sites were synthesized under hydrothermal conditions. In <b>1</b>, each [Mo₄O₁₄]^4- cluster connected with six neighboring [Mo₄O₁₄]^4- clusters through six binuclear [Cu₂(2-ptz)₂]²⁺ subunits to yield a two-dimensional (2D) layer. In <b>2</b>, bidentate inorganic [Mo₈O₂₆]^4- anions link the trinuclear [Cu₃(OH)₂(3-ptz)₄] clusters to construct a 1D chain. Adjacent chains connect through Mo-N bonds between the [Mo₈O₂₆]^4- anions and pyridyl groups from the trinuclear clusters to form a 2D layer. The effect of the N-donor sites of the rigid isomeric ligands on the structures of <b>1</b> and <b>2</b> was discussed. The electrochemical properties and photocatalytic activities of <b>1</b> and <b>2</b> have also been studied.</p></div

Transfer of Photoinduced Electrons in Anatase–Rutile TiO₂ Determined by Time-Resolved Mid-Infrared Spectroscopy

It has been a long-standing debate about the photogenerated charge transfer in anatase–rutile mixed phase TiO₂. In this work, we investigated this issue by studying anatase, rutile, and anatase–rutile mixed phase TiO₂ with time-resolved mid-IR (MIR) spectroscopy (TR-MIR) in a vacuum or methanol vapor. Anatase TiO₂ shows transient MIR absorption on microsecond time scale after 355 nm excitation, which is attributed to photoinduced electrons in the shallow states of anatase. Conversely, there is no transient MIR absorption detected for rutile TiO₂. For anatase–rutile mixed phase TiO₂, the initial MIR absorption intensity decreases relative to that calculated from its phase composition, indicating that electron transfer takes place in the anatase–rutile phase junction of mixed phase TiO₂. Our results suggest that the photogenerated electrons in the shallow states of anatase transfer to rutile across the anatase–rutile interface, but this does not exclude the possibility that the net electron transfer from rutile to anatase due to the complicated energy levels and kinds of trapped states in mixed phase TiO₂

Site-Specific Biomimetic Precision Chemistry of Bimodal Contrast Agent with Modular Peptides for Tumor-Targeted Imaging

Various biomimetic nanoparticles have been fabricated for cancer nanotheranostics with a diverse range of proteins. However, the operating mechanisms of these reactions are still unclear, especially on the interaction between metal ions and protein, the precise binding sites, and the existence format of nanoparticles. Assuming the shortening of the amino acids sequence into several, namely short peptides, it would be much easier to investigate the biomimetic reaction mechanism. In this study, a modular peptide, possessing Au³⁺ ion coordination motifs and a Gd³⁺ ion chelation sequence, is designed and synthesized. This peptide is experimentally found effective in site-specific biomimetic synthesis of paramagnetic fluorescent gold nanoclusters (pAuNCs) with a quantum yield of 6.8%, deep red emission at 676 nm, and potent relaxivity. The gel electrophoresis result declares that the two imaging motifs in pAuNCs are quite stable. In vivo fluorescence–magnetic resonance bimodal imaging show significant tumor enhancement by pAuNCs in tumor-bearing mice. In vivo biodistribution and toxicity studies reveal that pAuNCs can be gradually cleared from the body without damage. This study presents a modular peptide that can incubate multifunctional nanoparticles in a biomimetic fashion and hopefully provides a strategy for the investigation of the mechanism of protein-mediated biomimetic synthesis

Effect of solvent on the construction of Co(II) coordination polymers containing a semi-rigid bis(benzimidazole) derivative: syntheses, structures, and properties

<div><p> Two Co(II) coordination polymers, [CoL(npa)]·2H₂O (<b>1</b>) and [CoL(Hnpa)₂] (<b>2</b>) (L = 1,4-bis(5,6-dimethylbenzimidazole-1-yl)benzene, H₂npa = 5-nitroisophthalic acid), have been synthesized in different solvent systems and characterized by Infrared (IR) spectroscopy, elemental analysis, and powder and single crystal X-ray diffraction. Compound <b>1</b> was synthesized under solvothermal conditions with DMF as solvent and had a pair of L ligands adopting a <i>μ</i>₂-bridging mode and connecting two Co²⁺ cations to generate a 26-membered Co₂L₂ loop. The npa²⁻ link adjacent Co₂L₂ loops via a bis(monodentate) bridging mode to create a 1-D channel-like chain structure. Compound <b>2</b> was obtained under hydrothermal conditions, and the carboxylate of the monodeprotonated Hnpa⁻ adopt a <i>μ</i>₁-<i>η</i>⁰: <i>η</i>¹ coordination to connect adjacent Co²⁺ cations into a 2-D polymeric layer. The <i>μ</i>₂-bridging L ligands connect adjacent 2-D [Co(Hnpa)]_n polymeric layers into a 3-D NaCl-like framework. The Co²⁺ cations and the L ligands in compounds <b>1</b> and <b>2</b> exhibit different coordination geometries and conformations. Effects of solvents on the construction of Co(II) coordination polymers were investigated. In addition, the electrochemical behavior of carbon paste electrodes containing <b>1</b> and <b>2</b> and the thermal stabilities of <b>1</b> and <b>2</b> were investigated.</p></div

Four Cu(II)/Co(II) coordination polymers based on N,N′-di(3-pyridyl)sebacicdiamide: influence of different carboxylate ancillary ligands on structures and properties

<p>Four Cu(II)/Co(II) coordination polymers, [Cu(L)(BDC)(H₂O)]·3H₂O (<b>1</b>), [Cu(L)(DNBA)₂] (<b>2</b>), [Co(L)₂(DNBA)₂] (<b>3</b>), and [Co(L)(NIPH)(H₂O)]·H₂O (<b>4</b>) (H₂BDC = 1,4-benzenedicarboxylic acid, HDNBA = 3,5-dinitrobenzoic acid, H₂NIPH = 5-nitroisophthalic acid, L = N,N′-di(3-pyridyl)sebacicdiamide), have been synthesized under hydrothermal conditions. The structures of <b>1</b>–<b>4</b> have been determined by single-crystal X-ray diffraction analyses and <b>1</b>–<b>4</b> were further characterized by infrared spectroscopy and thermogravimetric analyses. Complex <b>1</b> is a 2-D polymeric layer with a 4-connected <i>sql</i> topology. Complex <b>2</b> displays a 1-D zigzag chain. Complex <b>3</b> possesses a 1-D double-chain structure. Complex <b>4</b> exhibits a ribbon chain based on the 1-D [Co–L]_n<i>meso</i>-helical chain. Adjacent layers for <b>1</b> and adjacent chains for <b>2</b>–<b>4</b> are further linked by hydrogen bonding or <i>π</i>–<i>π</i> stacking interactions to form 3-D supramolecular networks. The differences of carboxylates and metal ions show significant effect on the ultimate architectures of the four complexes. Thermal stabilities, fluorescent properties and photocatalytic activities of <b>1</b>–<b>4</b> were also studied.</p

Mechanical Properties and in Vitro and in Vivo Biocompatibility of a‑C/a-C:Ti Nanomultilayer Films on Ti6Al4V Alloy as Medical Implants

Hydrogen-free a-C/a-C:Ti nanomultilayer films are deposited on medical Ti6Al4V alloy using a closed field unbalanced magnetron sputtering under graded bias voltage. The mechanical and tribological properties of the nanomultilayer films are performed on the nanoindentor, Rockwell and scratch tests, and ball-on-disk tribometer. The biological properties are evaluated by cell cytotoxicity, genotoxicity, subchronic systemic toxicity and implant. The hard a-C/a-C:Ti nanomultilayer films on medical alloy exhibit high adhesion strength and excellent tribological properties in both ambient air and Hank’s solution. Biocompatibility results reveal the film no cytotoxity, no genotoxicity, no subchronic systemic toxicity and no contraindications in implant systems. Because of excellent mechanical properties and biosafety, the carbon-based films on medical alloy unveils a prospective application in medical implants